It takes less energy to raise the temperature of a block of aluminium by 1°C than it does to raise the same amount of water by 1°C. The amount of energy required to change the temperature of a material depends on the specific heat capacity of the material.

Heat capacity

The specific heat capacity of water is 4,200 Joules per kilogram per degree Celsius (J/kg°C). This means that it takes 4,200 J to raise the temperature of 1 kg of water by 1°C.

Some other examples of specific heat capacities are:

Material

Specific heat capacity (J/kg/°C)

Brick

840

Copper

385

Lead

129

Lead will warm up and cool down fastest because it doesn’t take much energy to change its temperature. Brick will take much longer to heat up and cool down. This is why bricks are sometimes used in storage heaters as they stay warm for a long time. Most heaters are filled with oil (1,800 J/kg°C) or water (4,200 J/kg°C) as these emit a lot of energy as they cool down and, therefore, stay warm for a long time.

curriculum-key-fact

The specific heat capacity of a material is the energy required to raise one kilogram (kg) of the material by one degree Celsius (°C).

Calculating thermal energy changes

The amount of thermal energy stored or released as the temperature of a system changes can be calculated using the equation:

Example

Sadie is experimenting with a model steam engine. Before the 0.25 kg of water begins to boil it needs to be heated from 20°C up to 100°C. If the specific heat capacity of water is 4,180 J/kg°C, how much thermal energy is needed to get the water up to boiling point?

Question

How much thermal energy does a 2 kg steel block (c = 450 J/kg°C) lose when it cools from 300°C to 20°C?

Question

How hot does a 3.5 kg brick get if it’s heated from 20°C by 20,000 J (20 kJ)?